linux-kernel - Re: [PATCHv1 7/8] arm64: dts: qcom: msm8998: Add PSCI cpuidle low power states

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Date:   Fri, 10 May 2019 17:11:01 +0200
From:   Marc Gonzalez <marc.w.gonzalez@...e.fr>
To:     Amit Kucheria <amit.kucheria@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     MSM <linux-arm-msm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv1 7/8] arm64: dts: qcom: msm8998: Add PSCI cpuidle low
 power states

On 10/05/2019 16:12, Amit Kucheria wrote:

> On Fri, May 10, 2019 at 6:45 PM Marc Gonzalez wrote:
>>
>> On 10/05/2019 13:29, Amit Kucheria wrote:
>>
>>> Add device bindings for cpuidle states for cpu devices.
>>>
>>> Cc: Marc Gonzalez <marc.w.gonzalez@...e.fr>
>>> Signed-off-by: Amit Kucheria <amit.kucheria@...aro.org>
>>> ---
>>>   arch/arm64/boot/dts/qcom/msm8998.dtsi | 32 +++++++++++++++++++++++++++
>>>   1 file changed, 32 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/qcom/msm8998.dtsi b/arch/arm64/boot/dts/qcom/msm8998.dtsi
>>> index 3fd0769fe648..208281f318e2 100644
>>> --- a/arch/arm64/boot/dts/qcom/msm8998.dtsi
>>> +++ b/arch/arm64/boot/dts/qcom/msm8998.dtsi
>>> @@ -78,6 +78,7 @@
>>>                        compatible = "arm,armv8";
>>>                        reg = <0x0 0x0>;
>>>                        enable-method = "psci";
>>> +                     cpu-idle-states = <&LITTLE_CPU_PD>;
>>
>> For some reason, I was expecting the big cores to come first, but according
>> to /proc/cpuinfo, cores 0-3 are part 0x801, while cores 4-7 are part 0x800.
>>
>> According to https://github.com/pytorch/cpuinfo/blob/master/src/arm/uarch.c
>>
>> 0x801 = Low-power Kryo 260 / 280 "Silver" -> Cortex-A53
>> 0x800 = High-performance Kryo 260 (r10p2) / Kryo 280 (r10p1) "Gold" -> Cortex-A73
> 
> Hmm, did I mess up the order of the big and LITTLE cores?
> I'll take a look again.

Sorry for being unclear. I was saying I expected the opposite,
but it appears the order in your patch is correct ;-)

Little cores have higher latency (+5%) than big cores?

Regards.